The “Irish lady” is a waitress in parliament’s ornate Pugin Room overlooking the River Thames, where Scotland’s former first minister is taking tea. She persists in asking Salmond if he would like some fruitcake, but it’s only half an hour before a lunch booking. He nearly succumbs, urging his aide to join him in a slice. Instead, Salmond’s aide says he’ll just have a glass of water. “You’re a cheap date,” Salmond giggles.

For someone who has spent his entire political life campaigning for Scottish independence, Salmond certainly seems to like being in Westminster. “I really enjoy it, this is a fantastic group of people,” smiles Salmond. “I make no bones about it, I’ve always loved the chamber of the House of Commons.”

This is Salmond’s second spell on the green benches, having represented Banff and Buchan on the north-east coast of Scotland for nearly a quarter of a century to 2010, when he decided to concentrate on being first minister.

When Nicola Sturgeon succeeded him after losing the independence vote by a surprisingly close 45% to 55% in 2014, rumours immediately circulated that he would seek a return to the Commons. In 2015, Salmond won Gordon, a Liberal Democrat stronghold since 1983, with a 25.5% increase in the SNP’s vote.

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Salmond seems to have been around for ever – his first stint as SNP leader, the party’s eleventh, started in September 1990 when Margaret Thatcher was prime minister – but he is still only a fairly youthful looking 61.

He would have been one of the Commons’ big beasts on his return, even if the SNP only had the six seats it held in the last parliament. But after the general election landslide that saw the party take 56 of the 59 constituencies available in Scotland, Salmond is now an alpha wolf with a large, well-organised pack.

He might not head that pack any more – Angus Robertson has been impressive as the Westminster leader since he took the post last year – but few doubt Salmond’s political pre-eminence. Ultimately leading the SNP’s first significant presence in Westminster, though, is another temptation that Salmond is resisting.

“Look, I’ve been leader of the Westminster group, I’ve been first minister of Scotland, I don't need any titles. I’ve done all that. My political ambitions are about trying to achieve independence.”

Instead, Salmond holds the SNP’s international affairs and Europe brief, an appropriate role for the party’s now semi-elder statesman. This is a post that pits his formidable political skills against the Brexit trio of foreign secretary Boris Johnson, international trade secretary Liam Fox and David Davis, the secretary of state for exiting the European Union. From this role, Salmond is convinced he can help the SNP force the second independence referendum the party so desperately craves.

Sturgeon has launched what she describes as “the biggest listening exercise in our party’s history”: a three-month consultation with more than two million Scots from September to 30 November – St Andrew’s Day – to try and build a consensus view on Scotland’s post-Brexit vote future.

Scotland voted overwhelmingly in favour of staying in the EU. Sturgeon has made it clear she does not believe an overall win for Brexit means there is a mandate for taking any part of the UK, let alone Scotland, out of the single market.

This is a red line or, as the SNP likes to put it, would be the “material change of circumstance” that Sturgeon and Salmond believe should result in that second independence referendum. But Salmond doubts Theresa May will heed this warning, given her tough stance on a range of policy issues, from grammar schools to immigration, since becoming prime minister in July.

Salmond says: “It’s possible the government could accept the first minister’s very reasonable demand that Scotland be kept within the single marketplace, which is her [Sturgeon’s] red line. But, my guess is that they won't do it, because there’s nothing about the prime minister’s disposition in her weeks in office that suggests she is at all flexible, sensitive, or responsive to Scotland’s legitimate claims … and therefore there will be a referendum.”

Salmond believes this referendum will take place during the two years of negotiations that will take place when the formal mechanism to facilitate Brexit, article 50 of the Lisbon treaty, is triggered next year.

Yet May has ruled out the possibility of a second independence referendum, arguing the previous result was “a very clear message” that Scotland wanted to remain in the UK. Salmond thinks this is just rhetoric. “It doesn’t matter,” he says. “I heard all that nonsense from David Cameron once upon a time. If the Scottish Parliament votes for a referendum, then there will be a referendum.

“David Cameron claimed that there wouldn't be a referendum, he said he wouldn't allow a referendum, and then faced with a parliamentary vote in Scotland for a referendum he acquiesced, as this prime minister will do.”

Intriguingly, he thinks this hypothetical referendum would have little impact on Brexit negotiations.

Salmond believes the complexity of leaving a bloc of which the UK has been a member for more than four decades will mean the unravelling of deals and pan-European legislation that will take years longer than the 24 months of article 50. In effect, the negotiations will result in little more than a heads of terms agreement.

“There will be virtually no detail whatsoever within the timescale of the negotiations,” says Salmond. “The purpose of an independence vote would be to keep Scotland within the European Union as an independent country. You would therefore have to change very little about Scotland’s relationship with Europe. It won't be affected by changes that haven't yet come into effect.”

Salmond also justifies another plebiscite by arguing unionists did not make clear that a vote to remain in the UK would “jeopardise” Scotland’s membership of the EU. The SNP’s landslides in Westminster and in the Scottish elections add weight to claims for a second referendum, he argues.

Much has been made by the SNP of a second referendum taking place when it is the “will of the Scottish people”. Salmond is in no doubt that time is now and practically dares his successor to call for an immediate vote.

“There have been six opinion polls since the European vote,” smiles the one-time Royal Bank of Scotland economist. “Three of which have shown a majority for independence and the other three have all shown an increase from 45% [support].

“Will Nicola Sturgeon push the button on a referendum if support for independence is, say, 50:50 or at that level? Well, I hit the button for a referendum when support was 27%. Why would she be reluctant on a much larger level than that?”

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Salmond’s answers are always drenched in political calculations. As well as being forced into letting the SNP have another crack at independence, Salmond reasons that May will have to drop the proposed boundary changes to reduce the number of MPs from 650 to 600.

It is thought that, based on 2015 election results, Labour would lose around 25 seats. Although this could increase the Conservative majority from 12 to around 40, plenty of Conservatives would lose their seats as well. Salmond believes the self-interest of these MPs, as well as Labour’s poor poll ratings and internal squabbling, will lead to the small rebellion that is needed to vote down the proposals.

“Boundary changes would [only] result in a Conservative advantage of 20 or so, maybe 30 [extra majority], so when you can see an opposition in complete and utter catastrophic disarray it’s not worth a candle,” argues Salmond.

Still, Salmond points out the SNP would be expected to win all but one Scottish seat if the changes took place. Clearly, he sees the forthcoming row as a win-win for the SNP: either the Conservatives tear themselves apart arguing or his party becomes even more dominant in Scotland.

And that’s the sort of calculation that can only please a man who likes to have his cake and eat it.